Glossary


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AGA

The AGA (Australian Gas Association) (http://www.aga.asn.au/) provides accredited product certfication services with respect to the Gas, Electrical and Plumbing sectors within Australia. It also provides additional certification services that are accepted by the relevant government/industry regulators.

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Appliance

An assembly, part of which uses gas to produce flame, heat, light, power or special atmosphere.

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Authorised Installer

A person appointed, licensed, authorised or otherwise permitted to carry out gasfitting work.

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Auto-Ignition Temperature

The lowest temperature at which the rate of self-heating of a gas-air mixture exceeds the rate of heat loss to the surroundings, thus causing the mixture to ignite.

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Automatic Ignition

The lighting of gas at a burner without a manual operation whenever gas flows from the burner.

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Bleed Line

A small diameter pipe or tube that conveys gas to a safe place from a gas component that discharges small rates of gas as part of its normal operation.

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Burner - Atmospheric

A system where all of the air for combustion is produced by the inspirating effect of the gas or the natural draught in the combustion chamber or combination of the two without mechanical assistance.

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Burner - Automatic

A burner system that, on starting, follows a self-acting sequence that has been manually or automatically initiated, to provide gas and ignition to the burner without any intermediate manual operation.

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Burner - Forced Draught

A system where all of the air, oxygen or a mixture of the two used for combustion is provided under pressure.

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Burner - Induced Draught

A system where all or part of the air for combustion is introduced by providing suction in the combustion chamber by mechanical means.

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Burner - Multi-Fuel

A burner that can use more than one fuel.

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Burner - Multi-fuel Alternative

A multi-fuel burner that can use only one fuel at a time.

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Burner - Mutli-Fuel Simultaneous

A multi-fuel burner that can use more than one fuel at a time.

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Burner - Part Automatic

A burner system that includes any self-acting operation.

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Burner Off Cycle

A normal cessation of operation occurring when a pre-determined operation condition is reached and the operation of the burner to provide the application of heat is no longer required. The equipment is placed into a safe stand-by condition ready to restart on demand; or a shut down to a safe stand-by condition in response to an incorrect condition signal resulting from a fault that is unlikely to be hazardous or is likely to be self rectifying so that normal restarting is permissible when the fault has cleared.

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Burner Unit

A number of burners, fed from the same manifold, controlled together, having one supervised ignition source and performing as a single burner.

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Closed Position Indicator Switch Related Phrases

A switch which indicates closed when the valve is within 1 mm of the closed position or has reduced the flow to 10% or less of the equivalent fully open flow for a given pressure differential.

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Combination Gas Control

An assembly of two or more different control functions in a single body.

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Combustion Product

Constituents resulting from the combustion of a fuel with air, oxygen or mixture of the two, including the inerts associated with the fuel and the air but excluding any other diluent or contaminant.

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Critical Time

The time required to build up a pocket or concentration of unignited gas of such quantity and proportions that, if ignited, the pressure of the resultant explosion could equal the permissible safe internal pressure of the appliance.

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Cross Lighting

Lighting of one burner from another either directly or by means of an intermediate flame.

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Damper

An adjustable device for controlling (a) air flow in a forced or induced draught air system; (b) the flow of flue products in a flue system; (c) the recirculation of air, flue gases or process gases; or (d) the flow of any other fluids.

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Direct-Fired Air Heater

An appliance for heating a forced air stream where the combustion products are released with the heated air.

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Direct-Fired Oven Heater

An oven in which the combustion products flow through the oven compartment.

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Double Block and Vent

See 'Safety Shut Off System Double Block and Vent'.

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Draught Diverter

A device, without moving parts, fitted in the flue of an appliance for isolating the combustion system from the effects of pressure changes in the secondary flue.

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Electronic Flame Safeguard

A flame safeguard utilising electronic components to perform its function.

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Excess Air

Air in excess of that required for complete combustion that is mixed unchanged with the combustion products, in the combustion chamber.

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Fail-Safe

A feature that ensures absence or malfunction of any critical control or safety component, system, signal or function will not result in an unsafe condition.

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Flame Abnormality

A flame condition that results in flame lift, floating, light back, appreciable yellow tipping, carbon deposition or objectionable odour.

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Flame Detector

A device that is sensitive to flame properties and initiates a signal when flame is detected.

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Flame Establishment Period

The period that begins when the fuel valve is energised and ends when the flame safeguard system is first required to supervise that flame.

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Flame Failure Response Time

The time taken for the flame safeguard to detect loss of flame and de-energise the safety shut off valve.

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Flame Lift

Separation of a flame from a burner port, whilst continuing to burn with its base some distance from the port.

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Flame Proving Period

The supervised period immediately following the flame establishment period and before any further operation other than shutdown is permitted.

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Flame Safeguard

A safety device that automatically cuts off the gas supply if the actuating flame is extinguished on the port.

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Flame Safeguard System

A system consisting of a flame detector(s) plus associated circuitry, integral components, valves and interlocks, the function of which is to shut off the fuel supply to the burner(s) in the event of ignition failure or flame failure.

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Flue

The pipe or duct through which combustion products are conveyed from a gas appliance to a discharge point, including any draught diverter, slip joint and associated duct, barometric device, fan or other fittings in the duct and includes the following.

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Flue - Common

A flue system designed to carry combustion products from two or more appliances.

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Flue - Natural Draught

A flue in which the draught is provided by the buoyancy effect of the hot gases in it.

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Flue - Open

A flue system containing a draught diverter or canopy.

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Flue - Secondary

The portion of the flue that extends from the outlet of the draught diverter to the flue terminal.

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Flue - Slip Joint

A join in the flue (usually close to the appliance) that may be dismantled to facilitate the disconnection of the appliance from the flue.

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Flue Gases

Combustion products plus all diluents and contaminants. These include, where applicable, excess air, dilution air, process air, and waste products from the process.

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Flue System

The passage through which flue gases are conveyed from an appliance to a discharge point including draught diverter, barometric device, fan or similar part.

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Flue Terminal

The point at which flue gases discharge from a flue.

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Forced or Induced Draught Combustion System

A combustion system where all or part of the air for combustion is provided by a fan or other mechanical device which is an integral part of the combustion system.

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Gas Consumption

The rate of energy consumed by an appliance under specific conditions and expressed in multipliers of joules per hour, for example, megajoules per hour (MJ/h) or gigajoules per hour (GJ/h).

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Gas Pressure Regulator

A device that automatically regulates the outlet pressure of the gas passing through it to a predetermined value.

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Gas Tight

Meets the leak testing requirements of the appropriate Standard.

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Gas/Air Ratio Control

A system which simultaneously controls the flow of gas and air to a burner(s).

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High Gas Pressure Detector

A sensing device that is actuated when pressure rises above a pre-set value in it.

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Hot Water Boiler

Any vessel wherein water is intended to be heated to a temperature exceeding 99C by the application of heat from the combustion products to the vessel without the generation of steam.

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Ignition Temperatureor

The lowest temperature at which heat is generated by combustion faster than heat is lost to the surroundings, and combustion thus becomes self-propagating.

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In Service

An appliance connected to the gas supply irrespective of the on or off status of the isolation valve.

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Indoor Flueless Appliance

An indoor appliance designed to discharge its combustion products into the same room or space in which it is installed.

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Injector

A device that causes air to mix with a stream of gas. In the case of an aerated burner it incorporates an orifice discharging gas into the mixing tube or throat.

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Interlock Boiler

A device or function that ensures that the operation of items of equipment is dependent upon the fulfilment of predetermined conditions by other items of equipment.

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Intermittent Pilot

A pilot that is automatically ignited each time the burner is started, and which is automatically extinguished with the main burner.

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Interrupted Pilot

A pilot that is automatically ignited each time the burner is started, and which is automatically extinguished at the end of the main flame establishment period.

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IP Rating

The IP Code (http://en.wikipedia.org/wiki/Ip_rating) (or Ingress Protection Rating, sometimes also interpreted as International Protection Rating) consists of the letters IP followed by two digits or one digit and one letter and an optional letter. As defined in international standard IEC 60529, IP Code classifies and rates the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in mechanical casings and with electrical enclosures.

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Leakage Detection System

A means of checking that the safety shut off valves and the vent valves, where fitted, of a safety shut off system are gas tight, also referred to as a valve proving system.

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Light Back

Transfer of the flame from burner port(s) into the body of the burner or back to the injector.

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Limit Device

A device that is actuated by the approach to a hazardous situation in an appliance due to abnormal conditions, and when actuated, causes the gas supply to all burners to shut off with lockout.

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Liquefied Petroleum Gas (LP Gas)

A gas composed predominantly of any of the following hydrocarbons, or any combination of them in the vapour phase; propane, propene (propylene), butane and butene (butylene).

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Liquefied Petroleum Gas (LP gas)

Liquefied petroleum gas (http://en.wikipedia.org/wiki/Liquefied_petroleum_gas)(also called LPG, GPL, LP Gas, or liquid propane gas) is a flammable mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles.

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Lockout

A safety shutdown condition of the control system that requires a manual reset in order to restart.

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Low-Gas-Pressure Detector

A sensing device that is actuated when the gas pressure falls below a pre-set value.

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Lower Explosive Limit (LEL)

The lowest percentage of gas in a mixture of gas and air in which combustion can be selfsustaining at standard temperature (15C) and pressure (101.325 kPa absolute) conditions.

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Manual Ignition

The lighting of gas at a burner by a manual operation whenever gas flows from the burner.

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Mixing Blower

A motor-driven blower, the suction side of which is supplied with a mixture of air and gas from an appropriate proportioning device, which supplies a burner(s) in the immediate vicinity of the blower and has no control and/or safety device between the blower and burner.

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Mixing Tube

That part of an atmospheric burner in which the air and gas are mixed.

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Modification

An upgrade to any or all of: gas valve train equipment; combustion/purge air system; flame safeguard system; burner management system (not involving like for like exchange of components) that changes the safety integrity of the existing system or takes the gas appliance out of its original certification criteria.

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Natural Draught

The flow produced by the tendency of warmed gases to rise are mixed.

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Natural Gas (NG)

A hydrocarbon gas consisting mainly of methane.

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No-Flow

A flow condition suitably below the normal proven air flow device setting that provides a reliable and repeatable no-flow signal from the flow device.

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Nominal Gas Consumption

The appliance gas consumption, in megajoules per hour, stated in specifications, data plates, instructions and general communications.

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Non-Return Valve

A device designed to operate automatically to prevent reversal of flow in a pipe.

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Open Flued Appliance

An indoor appliance designed to be connected to an open flue system, its combustion air being drawn from the room or space in which it is installed.

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Open Position Indicator Switch

A switch that indicates 'open when' the valve is within 10% of the fully open position.

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Operating Pressure

The gas pressure that the consumer piping or the appliance is or will be subjected to under normal operating conditions.

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OPSO Regulator

Over-Pressure Shut-Off (OPSO) Regulators (http://www.elstergasdepot.com/repair-parts/regulator-shut-off-parts/opso.html) prevent excessive gas pressure from entering a building causing a hazardous condition. The shut-off device closes if the regulator outlet pressure rises above the maximum set point or set pressure.

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Over-Pressure Protection System

A system preventing the pressure in piping or in an appliance from exceeding a predetermined value.

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Over-Temperature Cut-Out Device

A manual reset or non-resetting device that functions to shut off the gas supply to a burner or burners to pre-vent temperature from exceeding a predetermined level.

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Parts Per Million (PPM)

PPM (http://www.engineeringtoolbox.com/ppm-d_1039.html) is commonly used as a measure of small levels of pollutants in air, water, body fluids, etc.

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Permanent Pilot

A pilot that is intended to be permanently alight while the appliance is in service and that is controlled independently of the main burner.

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Pilot

A permanently located burner independent of the main burner, small in relation to it, and arranged to provide ignition for the main burner.

Position Indicator Switch

A switch that is activated when a particular position is reached.

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Position-Proving System

A means of checking that the safety shut off valves and vent valves of a double block and vent safety shut off system are in the correct position.

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Pressure

Pressure (the symbol: p or P) (http://en.wikipedia.org/wiki/Pressure) is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure (also spelled gage pressure) is the pressure relative to the local atmospheric or ambient pressure.

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Process After-Burner

A gas-fired appliance used specifically for the incineration of exhaust gases containing combustible gases or dust in concentrations below the lower explosive limit.

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Programmable Electronic System (PES)

A system based on one or more central processing units (CPUs), connected to sensors and/or actuators, for the purpose of control, protection or monitoring.

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Programming Flame Safeguard

A flame safeguard that automatically sequences at least two burner functions such as ignition spark, gas valve, etc.

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Proof-of-Closure Switch

A switch fitted to a safety shut off valve that is only activated after the valve is closed and incorporates over-travel of the valve past the position where the valve is just closed.

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Protected Pilot

A pilot that is fitted with a flame safeguard.

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Purge (or Purging)

With respect to an appliance means the removal of combustibles.

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Purge Volume

The purge volume includes the combustion chamber and all areas where combustion products and combustible vapours, dusts or gases may accumulate in the appliance or process, up to the vertical connection of a flue or chimney that discharges directly to atmosphere.

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Rated Working Pressure

The maximum allowable inlet pressure specified by the manufacturer.

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Relief Device

A safety device designed to forestall the development of a dangerous condition by preventing pressure, temperature or vacuum build-up.

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Safe Start Check

A check of a flame safeguard system that will prevent an ignition attempt from occurring if the system is in the flame proved condition before any gas valves are energised as part of an ignition attempt.

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Safety Shut Off System

An arrangement of valves and associated control systems that shuts off the supply of gas, when required, using a device that senses an unsafe condition.

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Safety Shut Off System, Double Block and Vent

A safety shut off system that incorporates two safety shut off valves in series, with the space between the two valves automatically vented. These valves are interlocked so that when the safety shut off valves are closed, the vent valve is open and vice versa.

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Safety Shut Off Valve

An automatic shut off valve that meets the requirements of AS 4629 and is used to shut off gas supply to an appliance when a signal is generated indicating the approach of an unsafe condition.

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Safety Shutdown

The action of shutting off all gas and ignition energy by means of a safety control such that restart cannot be accomplished without a full start cycle.

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Set Pressure

The mean pressure at which a device will actuate at a specific adjustment.

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Simulated Natural Gas (SNG)

A gas comprising a mixture of LP gas and air, in the approximate proportions of 55% LP gas and 45% air for commercial propane.

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Single Phase

Single Phase (http://en.wikipedia.org/wiki/Single_phase)electric power refers to the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single Phase distribution is used when loads are mostly lighting and heating, with few large electric motors.

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Solenoid Valve

A solenoid valve (http://en.wikipedia.org/wiki/Solenoid_valve)is an electromechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid.

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Start Gas

The gas flowing at a pilot burner, or when no pilot burner is fitted, at a main burner during the flame establishment period for initial ignition.

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Steam Boiler

Any vessel wherein steam is intended to be generated at a pressure above that of the atmosphere by the application of heat from the combustion products to the vessel.

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Stoichiometric Combustion

The theoretical combustion of fuel in air such that no combustible agent or residual oxygen remains in the combustion products.

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Supervised Burner

A burner fitted with a flame safeguard system.

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Temperature Limit Device

A device that automatically causes the gas supply to be interrupted when the temperature at the control point reaches a predetermined limit.

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Tempered Liquefied Petroleum Gas (TLP)

A gas comprising a mixture of LP Gas and air, in the approximate proportions of 27% LP Gas and 73% air for commercial propane.

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Test Firing Valve

A manual shut off valve that can be used for turning a burner on or off in order to test it for satisfactory ignition, flame stability, etc.

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Thermocouple

Thermocouples (http://en.wikipedia.org/wiki/Thermocouple) are a widely used type of temperature sensor for measurement and control and can also be used to convert a heat gradient into electricity. They are inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures.

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Thermostat

A device that automatically maintains a predetermined temperature in an appliance.

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Town Gas (TG)

A gas manufactured from coal or petroleum feedstocks.

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Transformer

An electrical transformer (http://www.ehow.com/how-does_5207362_electrical-transformers-explained.html) is a device that allows one voltage level to pass through it to be either increased or decreased.

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Type A Appliance

An appliance for which a certification scheme exists.

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Type B Appliance

An appliance, with gas consumption in excess of 10 MJ/h, for which a certification sheme does not exist.

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Valve

A device for the purpose of controlling or shutting off flow.

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Valve Train

A combination of valves, regulators, pipe pieces, unions and the like that form an integrated system for flow or pressure control and safe operation of a burner.

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Vent Line

A pipe that is connected to a gas pressure regulator, relief valve or a double block and vent safety shut off system, and will convey gas to a safe location.

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Vent Valve, Double Block and Vent Safety Shut Off System

A valve in the vent line of a double block and vent safety shut off system that automatically opens when de-energised and automatically closes when energised.

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